The Romania and Zimbabwe focused miner and developer said the new cash was needed "due to the continued delay" of the expected $5.5 million from Mercuria.
Vast closed on Tuesday at 35p (US44.3c) and opened at 22p, although caught up in early trading to 34p.
The company runs the Manaila copper and zinc mine in Romania and has 25% of the small Pickstone-Peerless gold mine in Zimbabwe, and is re-opening the Baita Plai polymetallic mine in Romania.
The Bergen Global Opportunity Fund convertible securities, divided in two tranches, are locked in for 30 days from issue, meaning they cannot be converted immediately, and Vast has a 90-day window to buy them back.
Vast will hold a shareholder meeting on issuing £1 million (US$1.27 million) in shares before the end of January, to "enable the company to raise additional capital, if needed, and to ensure that sufficient headroom is available for conversion".
The company said issuing more shares was not ideal but it could not see another way to continue work at brownfield project Baita Plai.
"We are cognisant of our previous statements that we would avoid raising finance through convertible securities with a conversion price linked to the share price at the date of conversion," said chairman Brian Moritz.
"We have only undertaken this transaction as a short-term bridge of a limited size pending the receipt of the expected $5.5 million Tranche B pre-payment finance from Mercuria, which we are expecting to complete within the 30-day period prior to the conversion rights on the convertible securities becoming effective."
Vast issued 68 million shares to Bergen as collateral, adding 1.1% to its total issued shares.